First Line of Defense: Immunology Basics [SEQ 1]
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Questions and Answers

What primary functions do skin and mucous membranes serve in the first line of defense against pathogens?

Skin acts as a physical barrier, while mucous membranes trap pathogens and provide an immune signaling function.

How do lysozymes in saliva contribute to innate immunity?

Lysozymes cleave glycosidic bonds in bacterial cell walls, weakening them and making bacteria susceptible to osmotic pressure.

Describe the role of AMPs like Psoriasin in the immune response.

AMPs destabilize bacterial membranes, leading to cell death, and sequester essential nutrients like zinc to inhibit bacterial growth.

What distinguishes innate immunity from acquired immunity in terms of response time and specificity?

<p>Innate immunity is rapid and nonspecific, while acquired immunity is slower, long-lasting, and highly specific to particular pathogens.</p> Signup and view all the answers

How does the acid pH in the stomach contribute to the body's defense mechanisms?

<p>The acidic pH in the stomach helps to kill ingested pathogens, functioning as a chemical barrier in the immune defense.</p> Signup and view all the answers

Study Notes

First Line of Defense

  • Physical Barriers:

    • Skin: A multi-layered barrier. The outer layer (epidermis) contains dead keratinocytes, providing a physical block to pathogens. The dermis, beneath the epidermis, includes immune cells. Skin's acidity (slightly acidic pH), high salt concentration, dryness, and constant shedding all impede microbial growth. Skin-produced antimicrobial peptides (AMPs) further contribute to defense.
    • Epithelial Linings: Mucous membranes and cilia in the nose, throat, and intestines create a physical barrier, trapping and expelling pathogens. Coughing, sneezing, vomiting are expulsive reflexes and mechanisms for removal of foreign material.
    • Normal Microflora: Naturally occurring bacteria on skin and in the gut help prevent colonization by harmful pathogens.

  • Chemical Barriers:

    • Low pH: Stomach acid (low pH) and skin acidity inhibit microbial growth. High salt concentrations in sweat also inhibit microbial growth.
    • Enzymes: Lysozymes, found in saliva and tears, target peptidoglycan causing bacterial cell walls to be damaged, resulting in osmotic pressure damage and bacterial death
    • Antimicrobial Peptides (AMPs): Skin, saliva, and other secretions contain AMPs like psoriasin, defensins, and lactoferricin. These peptides target bacterial membranes, disrupt their function, sequester essential nutrients, and ultimately kill bacteria or inhibit growth.

  • Psoriasin: Damages bacterial membranes by disrupting them, targeting Gram-negative bacteria selectively.

  • Defensins: Form pores in bacterial membranes, further leading to bacterial death. alpha-defensins are produced in immune cells while beta-defensins are found in skin and saliva.

  • Lactoferrin: Binds iron, depriving bacteria of this essential nutrient.

Innate Immunity

  • Innate immunity is a rapid, non-specific response.
  • Includes macrophages, natural killer (NK) cells, and dendritic cells.

Acquired Immunity

  • Acquired immunity is specific and long-lasting, involving B cells and T cells.

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Description

Explore the essential physical and chemical barriers that serve as our body's first line of defense against pathogens. This quiz covers the skin's protective role, epithelial linings, and the importance of normal microflora. Test your understanding of how these defenses work to keep us healthy.

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